Catalyst and method for preparing catalyst

ABSTRACT

A catalyst includes LTA zeolite including copper ions, wherein a Si/Al ratio of the LTA zeolite is 2 to 50. The catalyst is coated on a honeycomb carrier or a filter. The catalyst removes NOx from a reaction gas at 100° C. or above. The catalyst has an NOx conversion rate of 80% at 450° C. or above.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority to Korean PatentApplication Nos. 10-2016-0016512 and 10-2016-0165932 filed in the KoreanIntellectual Property Office on Feb. 12, 2016 and Dec. 7, 2016, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a method for manufacturing a zeolitecatalyst. More particularly, the present disclosure relates to a methodfor manufacturing a zeolite catalyst of which high-temperatureperformance can be improved.

BACKGROUND

In general, carbon monoxide, hydrocarbons, and nitrogen oxides areincluded as harmful materials in exhaust gas of diesel vehicles.Nitrogen oxides cause environmental problems such as photochemical smogand acid rain, as well as human diseases. Therefore, there is a demandfor improving engines and developing a post-treatment technology ofexhaust gas.

The most effective technology for removing nitrogen oxides uses aselective catalytic reduction (SCR) method. This method has beendeveloped according to a reducing agent such as ammonia (NH3), urea,hydrocarbon (HC), and the like, and various catalysts. Ammonia (NH₃) hasbeen known to be effective in removing nitrogen oxides from a fixedobject such as a power plant and an incinerator. Since there is aproblem of storage/transport and use of ammonia, in case of a movingobject such as a vehicle, urea has been known to be effective as it iscapable of being easily decomposed to ammonia by heat decomposition anda hydration reaction.

As the catalyst for use in the selective catalyst reduction method,zeolite-based catalysts such as copper (Cu)/zeolite having excellentfunctions has been developed.

In particular, high temperature activity of such a catalyst is importantin treatment of high-temperature exhaust gas.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention, andtherefore, it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY

The present disclosure has been made in an effort to provide a methodfor manufacturing a zeolite catalyst of which high-temperatureperformance can be improved.

A catalyst according to an exemplary embodiment of the presentdisclosure includes linde type A (LTA) zeolite including copper ions,wherein an Si/Al ratio of the LTA zeolite is 2 to 50.

The catalyst may be coated on a honeycomb carrier or a filter.

The catalyst may remove NOx from a reaction gas at 100° C. or above.

The catalyst may have an NOx conversion rate of 80% at 450° C. or above.

A content of copper in the catalyst may be 1 wt % to 5 wt %.

The catalyst may further include an additive.

The additive may be an alkali metal or an alkali earth metal, and aratio of the additive and aluminum may be 0.1 to 0.3.

The additive may be selected from a group consisting of La, Ce, Zr, Sc,and In, and the ratio of the additive and aluminum may be 0.01 to 0.05.

The catalyst may further include a copper type of SSZ-13 zeolite.

A mixing ratio of the LTA zeolite and the copper-type SSZ-13 zeolite maybe 1:3 to 3:1.

According to another exemplary embodiment, a catalyst includes LTAzeolite that contains Fe ions, wherein an Si/Al ratio of the LTA zeoliteis 2 to 50.

The catalyst may be coated on a honeycomb carrier or a filter.

The catalyst may remove NOx from a reaction gas at 100° C. or above.

A content of iron in the catalyst may be 1 wt % to 5 wt %.

Accordig to another exemplary embodiment of the present disclosure, amethod for manufacturing a catalyst includes: preparing a LTA zeolite ofwhich a Si/Al ratio is 2 or more; preparing s LTA zeolite containingions by using the LTA zeolite; and preparing a copper-type of LTAzeolite by performing copper ion exchange on the ion-containing LTAzeolite.

A Si/Al ratio of the LTA zeolite may be 2 to 50.

The preparing of the ion-containing LTA zeolite may include substitutingions in the LTA zeolite.

The preparing of the ion-containing LTA zeolite may include adding theLTA zeolite to an ammonium salt for reaction and then drying the LTAzeolite, wherein the ammonium salt may be ammonium nitrate (NH₄NO₃).

The performing of copper ion exchanging on the ion-containing LTAzeolite may include adding the ion-containing LTA zeolite to a copperprecursor solution and stirring the solution.

The method for manufacturing the catalyst may further include thermallytreating the copper type of LTA zeolite after the preparing of thecopper-type LTA zeolite, wherein the thermal treatment may be performedat a temperature ranging from 1 to 30° C./min from 400 to 750° C.

The preparing of the LTA zeolite having the Si/Al ratio of 2 or more mayinclude preparing the LTA zeolite using an LTA seed or not using an LTAseed.

According to another exemplary embodiment of the present disclosure, amethod for manufacturing a catalyst includes: preparing an LTA zeoliteof which a Si/Al ratio is 2 or more; preparing an LTA zeolite containingions using the LTA zeolite; and preparing an iron type of LTA zeolite byperforming iron (Fe) ion exchange on the ion-containing LTA zeolite.

The preparing of the Fe ion exchange on the ion-containing LTA zeolitemay include adding the ion-containing LTA zeolite to an iron precursorsolution and stirring the solution.

The preparing of the ion-containing LTA zeolite may include adding theLTA zeolite to an ammonium salt for reaction and then drying the LTAzeolite, wherein the ammonium salt may be ammonium nitrate (NH₄NO₃).

The performing of the Fe ion exchange on the ion-containing LTA zeolitemay further include: mixing the ion-containing LTA zeolite with at leastone of iron(III) nitrate nonahydrate (Fe(NO₃)₃.9H₂O), sulfuric acidhydrate (FeSO₄.7H₂O), iron(II) oxalate dihydrate (FeC₂O₄.2H₂O), andiron(III) chloride tetrahydrate (FeCl₂.4H₂O); and stirring the mixture.

The method for manufacturing the catalyst may further include thermallytreating the Fe-type of LTA zeolite the performing of the Fe ionexchange on the ion-containing LTA zeolite, wherein the thermaltreatment may be performed at a temperature ranging from 1 to 30° C./minfrom 400 to 750° C.

The preparing of the LTA zeolite having the Si/Al ratio of 2 or more mayinclude preparing a LTA zeolite using an LTA seed or not using an LTAseed.

As described, according to the method for manufacturing the zeolitecatalyst according to the exemplary embodiment, acidity is low and thusthe high-temperature performance of the catalyst can be improved whilereducing the consumption of urea.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a structure of an LTA zeolite according to anexemplary embodiment of the present disclosure.

FIG. 2 is a graph illustrating a measurement result of removal ofnitrogen oxide of a zeolite catalyst in various temperature rangesaccording to an exemplary embodiment of the present disclosure and acomparative example of the present disclosure.

FIG. 3A is a measurement result of an NOx conversion ratio in a freshstate, and FIG. 3B is a measurement result of the NOx conversion ratioafter performing hydro-thermal aging at 75° C.

FIG. 4 shows a NOx conversion ratio of a catalyst according toExperimental Example 3.

FIG. 5 to FIG. 7 show a NOx conversion ratio of a catalyst according toExperimental Example 4.

FIG. 8 and FIG. 9 show a NOx conversion ratio of a catalyst according toExperimental Example 5.

FIG. 10 to FIG. 13 show a NOx conversion ratio of a catalyst accordingto Experimental Example 6.

FIG. 14 to FIG. 17 show a NOx conversion ratio of a catalyst accordingto Experimental Example 7.

FIG. 18 to FIG. 21 show a NOx conversion ratio of a catalyst accordingto Comparative Example 1.

FIG. 22 shows a NOx conversion ratio of a catalyst according toComparative Example 1.

FIG. 23 is a block diagram of an exhaust gas purification device thatemploys the zeolite catalyst according to an exemplary embodiment of thepresent disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsare shown. As those skilled in the art would realize, the describedembodiments may be modified in various different ways, all withoutdeparting from the spirit or scope of the present disclosure.

The drawings and description are to be regarded as illustrative innature and not restrictive, and like reference numerals designate likeelements throughout the specification.

In addition, unless explicitly described to the contrary, the word“comprise” and variations such as “comprises” or “comprising” will beunderstood to imply the inclusion of stated elements but not theexclusion of any other elements.

Hereinafter, a method for manufacturing a catalyst according to anexemplary embodiment of the present disclosure will be described indetail. A catalyst manufactured in the present exemplary embodiment maybe a zeolite catalyst.

A method for preparing zeolite for manufacturing the catalyst accordingto an exemplary embodiment of the present disclosure will be described.

First, LTA zeolite is prepared. In preparation of the LTA zeolite, aseed may or may not be used. A Si/Al ratio of the LTA zeolite preparedin the present stage may exceed 1. More specifically, the Si/Al ratiomay be 2 to 50. Preferably, the Si/Al ratio may be 5 to 30. Morepreferably, the Si/Al ratio may be 8 or more.

As an example, a process for preparing the LTA zeolite using the seedwill be described.

In order to prepare the LTA zeolite, an LTA seed is mixed in a mixtureof aluminum hydroxide (Al(OH)₃) and tetraethyl orthosilicate(Si(OC₂H₅)₄).

Specifically, a 1,2-dimethyl-3-(4-methylbenzyl)imidazolium hydroxideaqueous solution and aluminum hydroxide (Al(OH)₃) are mixed and themixture is primarily stirred, and then tetramethylammonium hydroxidepentahydrate is additionally mixed and then secondarily stirred so as toprepare a first mixture.

Here, with respect to the total weight of the first mixture, 20 to 35 wt% of 1,2-dimethyl-3-(4-methylbenzyl)imidazolium hydroxide, 1 to 2 wt %of aluminum hydroxide (Al(OH)₃), 1 to 5 wt % of tetramethylammoniumhydroxide pentahydrate, and a residual quantity of water are mixed, andthe primary stirring and the secondary stirring may be respectivelyperformed for about 0.5 to 1.5 h.

Tetraethyl orthosilicate (TEOS) (Si(OC₂H₅)₄) is mixed into the firstmixture and then third stirring is performed, and then the LTA seed ismixed and fourth stirring is performed so as to prepare a secondmixture.

30 to 35 wt % of TEOS may be mixed with respect to the total weight ofthe second mixture, and the amount of LTA seed may be 2 to 6 wt % withrespect to the total weight of the entire silicon included in the LTAzeolite.

In addition, the third stirring may be performed for about 2 to 4 h, andthe fourth stirring may be performed for about 20 to 28 h.

Next, the second mixture is sufficiently heated to cause hydrolysis ofthe TEOS, and ethanol and water generated from the hydrolysis of TEOSare evaporated such that a third mixture is prepared.

The second mixture may be heated at a temperature between 70° C. and 90°C.

Next, a hydrofluoric aqueous solution is mixed in the third mixture, anda fourth mixture is prepared through heating, cleansing, and dryingprocesses.

Here, the third mixture may be heated for a constant time period at atemperature of about 150° C. to 200° C., the cleansing process may beiteratively performed, and the drying process may be performed at roomtemperature.

Next, heat treatment is additionally performed to remove an organicmaterial from the fourth mixture such that the LTA zeolite formanufacturing the zeolite catalyst according to an exemplary embodimentof the present disclosure is manufactured.

The heat treatment may be performed at a temperature between 500° C. and700° C. for about 6 to 10 h, and a Si/Al ratio of the LTA zeolite may be2 to 50 in the present exemplary embodiment.

When the LTA zeolite is prepared without using the seed, the LTA zeolitecan be prepared as follows. As organic structure-inducing molecules, 0.0mol to 0.2 mol of aluminum hydroxide and 0.0 mol to 0.2 mol oftetramethylammonium hydroxide (hereinafter referred to as TMAOH) areadded in 0.1 mol to 1.0 mole of1,2-dimethyl-3-(4-methylbenzyl)imidazolium hydroxide (hereinafterreferred to as 12DM3 (4MB)IOH) in a plastic beaker and then sufficientlystirred. Next, tetraethyl orthosilicate (hereinafter referred to asTEOS) is added to the reactants in a proportion of 1 mol, and themixture is sufficiently stirred.

Next, the solution is sufficiently heated at 60° C. to 100° C. until theamount of ethanol generated due to hydrolysis of TEOS added to thesolution is completely removed, and at the same time the amount of wateris 0 to 10 mol. Then, when 0.1 to 1.0 mol of hydrogen fluoride (HF) isadded and sufficiently mixed, a reaction mixture having Chemical Formula1 is obtained.1 SiO₂:0.0-0.2 Al(OH)₃:0.0-0.2 TMAOH:0.1-1.0 R:0.1-1.0 HF:0-10H₂O  [Chemical Formula 1]

wherein R denotes 12DM3 (4MB)IOH.

The reaction mixture is then moved to a Teflon reactor, and placed in acontainer that is made of stainless steel again and heated at 100° C. to200° C. for 0.1 to 14 d to prepare the LTA zeolite. The LTA zeoliteprepared by the above method may also have a Si/Al ratio of 2 to 50.However, the above-described manufacturing method is illustrative and isnot limited to as above-described.

An XRD pattern of the LTA zeolite manufactured in the present stage isshown in the lower part of FIG. 1. A structure of the LTA zeolitemanufactured in the present stage is shown in the upper part of FIG. 1.

Next, a step of preparing LTA zeolite containing ions using themanufactured LTA zeolite will be described in detail.

First, LTA zeolite is placed into an ammonium salt, refluxed, washed,and dried to manufacture an NH₄-type LTA zeolite containing NH₄+ ions.

Here, the ammonium salt may be ammonium nitrate (NH₄NO₃).

The reflux process can be carried out at a temperature of 60 to 100° C.for 5 to 7 h.

In the present embodiment, ammonium ions are exemplarily described asthe ions, but the present disclosure is not limited thereto. That is,use of other ions and ion salts is also included within the scope ofthis disclosure.

Then, LTA zeolite including ions undergoes copper (Cu) ion exchange suchthat a Cu type of LTA zeolite including copper ions is prepared.

For the copper ion exchange, the LTA zeolite ions is injected into acopper precursor solution such as copper acetate monohydrate, coppernitride, copper nitrate, copper sulfate, and the like, and stirred, andthen cleansing and drying processes are performed such that the Cu typeof LTA zeolite can be prepared.

As a possible alternative, the LTA zeolite including ions may undergoesiron (Fe) ion exchange such that a Fe type of LTA zeolite including Feions can be prepared in another exemplary embodiment of the presentdisclosure.

The performing of the Fe ion exchange can be carried out by mixing theLTA zeolite including ions with at least one of iron(III) nitratenonahydrate (Fe(NO₃)₃.9H₂O), sulfuric acid hydrate (FeSO₄.7H₂O),iron(II) oxalate dihydrate (FeC₂O₄.2H₂O), and iron(III) chloridetetrahydrate (FeCl₂.4H₂O) and stirring.

Next, the Cu type of LTA zeolite or the Fe type of LTE zeolite is heatedin an oven with a gradually increasing temperature, and then a heattreatment process is performed such that the zeolite catalyst accordingto an exemplary embodiment of the present disclosure is manufactured.

Here, for the heat temperature of the Cu type of LTA zeolite or the Fetype of LTE zeolite, the temperature may be increased to 400 to 750° C.at a rate of 1 to 30° C./min, and then the heat treatment may beperformed to about 1 to 24 h.

Hereinafter, experimental examples of the present disclosure will bedescribed. However, the following experimental examples are onlyexemplaries, and the present disclosure is not limited to the followingexperimental examples.

Experimental Example: LTA Zeolite Catalyst Preparation

1 LTA Zeolite Preparation

In a plastic beaker, with respect to the total weight of an aqueoussolution, 29.4 wt % (12.38 g) of1,2-dimethyl-3-(4-methylbenzyl)imidazolium hydroxide aqueous solutionand 0.1733 g of aluminum hydroxide were mixed and then stirred for about1 h, and then tetramethylammonium hydroxide pentahydrate at 0.4152 g wasadditionally mixed therein and then stirred for about 1 h.

Next, tetraethyl orthosilicate (TEOS) at 6.80 g was mixed therein andthen stirred for about 3 h, 4 wt % of LTA seed with respect to theentire silica injected thereto was added thereto and then stirred forabout 24 h, and the mixture was heated at 80° C. to cause hydrolysis ofthe TEOS such that 5.90 g of ethanol and 5.37 g of water generated fromthe hydrolysis were evaporated.

Next, with respect to the total weight of the aqueous solution, 48 wt %(0.577 ml) of a hydrofluoric aqueous solution was mixed therein.

Then, the mixture to which the hydrofluoric aqueous solution was addedwas injected into a steel container and then heated at 175° C. for about17 h while rotating the container at a speed of 60 rpm such that a solidproduct was generated, and the solid product was iteratively cleansedand then dried at room temperature.

In order to remove an organic material from the dried mixture, the driedmixture was heat-treated at 600° C. in a muffle furnace for about 8 h tothereby manufacture an LTA zeolite, XRD analysis was performed on themanufactured zeolite to determine that the zeolite had an LTA structure,and a Si/Al ratio was determined to be 16 through ICP analysis.

2. Zeolite Catalyst Preparation

2 g of the manufactured LTA zeolite and 100 ml of 1 M ammonium nitratewere mixed in a two-neck flask, and the mixture was refluxed at 80° C.for about 6 h.

Next, the mixture was iteratively cleansed with a filter and distilledwater and then dried at room temperature, and the cleansing and dryingprocesses were repeated two times such that an NH₄ type of LTA zeolitewas manufactured.

The dried NH₄ type of LTA zeolite was injected into 100 ml of a 0.01 Mcopper acetate monohydrate (Cu(OAc)₂.H₂O) solution and then stirred atroom temperature for about 6 h.

The dried NH₄ type of LTA zeolite was injected into 100 ml of a 0.01 Mcopper acetate monohydrate (Cu(OAc)₂.H₂O) solution and then stirred atroom temperature for about 6 h.

In order to determine a removal rate of nitrogen oxide in the zeolitecatalyst according to an exemplary embodiment of the present disclosure,an experiment was performed to measure a removal rate of the nitrogenoxide by temperature, and a result of the experiment is shown in FIG. 2.

FIG. 2 is a graph illustrating a result of an experiment performed tomeasure a removal rate of nitrogen oxide in the zeolite catalystaccording to an exemplary embodiment of the present disclosure and in azeolite catalyst according to a comparative example in varioustemperature ranges.

In FIG. 2, the horizontal axis denotes a temperature (° C.) and thehorizontal axis denotes a removal rate (%) of nitrogen oxide.

As the zeolite catalyst according to a comparative example, Cu/SSZ-13(Si/Al=13) was used.

In order to determine high-temperature performance of the zeolitecatalyst according to an exemplary embodiment of the present disclosure,two zeolite catalysts, one with no treatment (Exemplary Embodiment 1)and the other one having undergone heat treatment at 750° C. for about24 h with air containing 10% humidity (Exemplary Example 2), wererespectively used in experiments.

In addition, in order to determine high-temperature performance ofCu/SSZ-13, two catalysts, one with no treatment (Comparative Example 1)and the other one having undergone heat treatment at 750° C. for about24 h with air containing 10% humidity (Comparative Example 2), wererespectively used in experiments.

In order to determine a removal rate by temperature, the zeolitecatalysts of the exemplary embodiments and the comparative examples weresupplied with 500 ppm of nitride oxide (NO), 500 ppm of ammonia (NH₃),5% of oxygen, and humidity of 10% at a gas hourly space velocity (GHSV)of nitrogen (N₂) of 100,000, and a removal rate of nitrogen oxide wasmeasured while changing the temperature between 150° C. and 550° C.

First, referring to FIG. 2, the nitrogen oxide removal rate of ExemplaryEmbodiment 1 is similar to that of Comparative Example 1 until thetemperature reaches 400° C., but when the temperature exceeds 400° C.,the nitrogen oxide removal rate of Exemplary Embodiment 1 is excellentcompared to Comparative Example 1.

In addition, in Exemplary Embodiment 2, the nitrogen oxide removal ratewas about 30% better than Comparative Example 2 from a zone where thetemperature exceeds 300° C.

Hereinafter, a catalyst according to an exemplary embodiment will bedescribed. A catalyst according to the present exemplary embodimentincludes LTA zeolite that contains copper ions, and a Si/Al ratio of theLTA zeolite may be 2 to 50. The catalyst may be coated on a honeycombcarrier or a filter.

In the catalyst according to the present exemplary embodiment, a Si/Alratio of the LTA zeolite may be 2 to 50. When the Si/Al ratio is lessthan 2, the hydrothermal stability may be poor, and when the Si/Al ratiois 50 or more, there may be a problem of low performance because thereare few aluminum sites that may contain Cu or Fe.

The catalyst can be manufactured by a manufacturing method according tothe present exemplary embodiment. The catalyst can remove NOx from areaction gas at a temperature of 100° C. or more.

In addition, as shown in FIG. 1, the catalyst according to the presentexemplary embodiment may have a NOx conversion ratio of above 80% at atemperature above 450° C.

In the catalyst, a copper/aluminum ratio may be 0.1 to 0.6.Alternatively, an amount of copper in the catalyst may be 1 wt % to 5 wt%. When the copper content is set to 2 wt % in a catalyst having a Si/Alratio of 23, even when hydrothermal aging is performed at a hightemperature of 900° C. or more for 24 h, excellent NOx purificationefficiency is exhibited. In the present disclosure, the termhydrothermal means a process to send a flow of air of relative humidity10% at a predetermined temperature and time.

In addition, in the exemplary embodiment, the catalyst may furtherinclude an additive. The additive may include an alkali metal or analkaline earth metal. Alternatively, the additive may be selected from agroup consisting of La, Ce, Zr, Sc, and In, and in this case, catalystperformance at low temperatures can be improved.

When the additive is an alkali metal or alkaline earth metal, the ratioof additive/aluminum may range from 0.1 to 0.3. When the additive is oneor more selected from the group consisting of La, Ce, Zr, Sc, and In,the ratio of additive/aluminum may range from 0.01 to 0.05.

In addition, the catalyst according to an embodiment of the presentdisclosure may be a mixture of copper-type LTA zeolite and copper-typeSSZ-132 zeolite. In this case, a mixing ratio of the copper-type LTAzeolite to the copper-type SSZ-13 zeolite may be 1:3 to 3:1. The mixingratio of the copper-type LTA zeolite to the copper-type SSZ-13 zeolitemay be 1:1. When the copper type LTA zeolite and the copper type SSZ-13are mixed and used, a NOx purification rate at a low temperature can beimproved.

As described above, the LTA zeolite catalyst according to the presentdisclosure has a Si/Al ratio of 2 to 50. Depending on a freshness stateor a hydrothermal aging temperature and time, the Si/Al ratio thatindicates optimum performance may be varied.

The effect of the LTA zeolite catalyst according to the variousexemplary embodiments of the present disclosure will now be describedwith reference to the following experimental examples.

Experimental Example 2: Measurement of NOx Conversion Rate

NOx conversion rates of copper-type LTA zeolite (▪) having a Si/Al ratioof 11, copper-type LTA zeolite (●) having a Si/Al ratio of 16, andcopper-type SSZ-13 zeolite (▴) having a Si/Al ratio of 16 according totemperature were respectively measured, and the measurement results areshown in FIG. 3. FIG. 3(a) shows a measurement result of the NOxconversion rate in a fresh state, and FIG. 3 shows a measurement resultof the NOx conversion rate after performing hydrothermal aging at 750°C.

In this case, the conversion rate was measured under the same conditionsas Experimental Example 1. That is, the catalyst was supplied with 500ppm of nitride oxide (NO), 500 ppm of ammonia (NH₃), 5% of oxygen, andhumidity of 10% at a gas hourly space velocity (GHSV) of nitrogen (N₂)of 100,000, and a removal rate of nitrogen oxide was measured whilechanging the temperature between 150° C. and 550° C. This is the same inother experimental examples below.

Referring to FIGS. 3(a) and (b), the LTA catalyst according to thepresent disclosure had an excellent NOx conversion rate beforehydrothermal aging, and the NOx conversion rate was remarkably improvedeven at a high temperature after hydrothermal aging at 750° C.

Experimental Example 3: LTA Zeolite Catalyst Having Copper Content of 2wt % and Si/Al Ratio of 23

In LTA zeolite having a Si/Al ratio of 23, manufactured according to thepresent disclosure, a copper content in copper ion exchange was set to 2wt %. With respect to such a catalyst, hydrothermal aging was carriedout at various temperature and time conditions, and NOx conversionperformance was measured and measurement results are shown in FIG. 4.Referring to FIG. 4, it was determined that even when hydrothermal agingwas performed for 24 h at 900° C., excellent NOx conversion performancewas maintained at 50% or more.

Experimental Example 4: Catalyst Including Additive

In LTA zeolite having a Si/Al ratio of 16, manufactured according to thepresent disclosure, NOx conversion rates were measured while variousadditives were added, and measurement results are shown in FIG. 5 toFIG. 7. FIG. 5 shows a result of adding an alkali metal or an alkalineearth metal as an additive, FIG. 6 shows a result of adding a La-basedmetal as an additive, and FIG. 7 shows a result of adding Zr, Sc, and Inas an additive. Referring to FIG. 5 to FIG. 7, it was determined that,when various additives are added, NOx conversion performance at a lowtemperature was improved without significantly affecting the NOxconversion performed at a high temperature.

Experimental Example 5: Mixed with Cooper-Type of SSZ-13 Zeolite

A catalyst was prepared by varying a mixing ratio of the LTA zeolitehaving a Si/Al ratio of 16, manufactured according to the presentdisclosure and a copper-type SSZ-13 zeolite, and NOx conversionperformance according to temperature was measured and measurementresults are shown in FIG. 8 and FIG. 9. FIG. 8 shows a measurementresult of NOx conversion performance in a fresh state, and FIG. 9 showsa measurement result of NOx conversion performance after hydrothermalaging at 900° C. for 12 h.

Referring to FIG. 8 and FIG. 9, performance was excellent as the contentof copper-type of SSZ-13 zeolite was high in the case of the freshcatalyst, and performance was excellent as the content of thecopper-type of zeolite was high. When all the results shown in FIG. 8and FIG. 9 are taken into account, it can be determined that theperformance was excellent in the case where the mixing ratio ofcopper-type LTA zeolite to copper-type SSZ-13 zeolite was 1:1 to 3:1.

Experimental Example 6: Experiment with Different Si/a Ratios

A NOx conversion rate according to temperature was measured by varying aSi/Al ratio of the LTA zeolite catalyst according to the presentdisclosure. The NOx conversion was measured by varying the agingtemperature of the catalyst in a fresh state, to 750° C., 850° C., and900° C., respectively, and measurement results are shown in FIGS. 10 to13. FIG. 10 shows performance at the fresh state, FIG. 11 showsperformance at the state of aging at 750° C., FIG. 12 shows performanceat the state of aging at 850° C., and FIG. 13 shows performance at 900°C. In FIG. 10 to FIG. 13, a content of copper was set to make a Cu/Alratio become 0.5.

Referring to FIG. 10 to FIG. 13, it could be determined that the ratioof Si/Al, which shows optimum activity depending on aging temperature,was different for each catalyst. Therefore, a person skilled in the artcan appropriately use the Si/Al ratio optimum for the conditions of useof the catalyst.

Experimental Example 7: Experiment with Different Si/Al Ratios

The experiment was performed using a method that is similar toExperimental Example 6, except that a reaction temperature wasconsistent, and NOx conversion rates according to a Si/Al ratio of acatalyst are shown in FIG. 14 to FIG. 17. FIG. 14 shows performance at afresh state, FIG. 15 shows performance in a state of aging at 750° C.,FIG. 16 shows performance in a state of aging at 850° C., and FIG. 17shows performance in a state of aging at 900° C.

As a result, the performance was excellent when the Si/Al ratio was lowat a low temperature in the case of the fresh catalyst, but theperformance was excellent when the Si/Al ratio was high at a hightemperature.

In addition, referring to FIG. 15 to FIG. 17, in the aging state, theperformance was excellent when the Si/Al ratio was 10 to 30.

Comparative Example 1: Experiment with Different Si/Al Ratios withRespect to Cu-type of SSZ-13 Catalyst

Comparative Example 1 is similar to Experimental Example 7, except thatrather than the LTA zeolite of the present disclosure, SSZ-13 zeolitewas used, and NOx conversion rates according to Si/Al ratios at eachtemperature were measured and measurement results are shown in FIG. 18to FIG. 21. FIG. 18 shows performance in a fresh state, FIG. 19 showsperformance in a state of aging at 750° C., FIG. 20 shows performance ina state of aging at 850° C., and FIG. 21 shows performance in a state ofaging at 900° C.

In comparison between the measurement results of Comparative Example 1shown in FIG. 18 to FIG. 21 and the measurement results of ExperimentalExample 7 shown in FIG. 14 to FIG. 17, the result of Comparative Example1 shows that high-temperature performance at 500° C. was relatively lowcompared to that of the LTA zeolite according to the present disclosure.In addition, in comparison with the results of Comparative Example 1,shown in FIG. 20 and FIG. 21 and the results of Exemplary Embodiment 7shown in FIG. 16 and FIG. 17, performance was significantly differentafter aging at 850° C. or above. That is, compared to the SSZ-13catalyst, the LTA zeolite catalyst according to the exemplary embodimentof the present disclosure shows a remarkably improved effect even whenthe Si/Al ratio is the same as that of the SSZ-13 catalyst.

In addition, a catalyst according to another exemplary embodimentincludes LTA zeolite that contains Fe ions, and a Si/Al ratio of the LTAzeolite may be 2 to 50. The catalyst may be coated on a honeycombcarrier or a filter, and the catalyst can remove NOx from a reaction gasat 100° C. or above. The catalyst may include ions at a content of 1 wt% to 5 wt %.

Experimental Example 8: LTA Zeolite Catalyst Containing Fe

LTA zeolite having a Si/Al ratio of 16 according to the presentdisclosure was prepared. In this case, Fe ions were added to the LTAzeolite such that an Fe-type of LTA zeolite having an Fe/Al ratio of 0.2was prepared. In addition, as a comparative example, SSZ-13 zeolitecontaining Fe ions was prepared.

With respect to the Fe-type of LTA zeolite catalyst (exemplaryembodiment) and the Fe-type of SSZ-13 zeolite catalyst, NOx conversionrates with respect to each temperature were measured and measurementresults are shown in FIG. 22. The conversion rate of each catalyst in afresh state and the conversion rate after hydrothermal aging at 850° C.were measured.

Referring to FIG. 22, it could be determined that the Fe-type of LTAzeolite catalyst according to the present disclosure has remarkablyimproved performance after hydrothermal aging at 850° C. compared to theFe-type of SSZ-13 zeolite catalyst.

Hereinafter, an example of application of the zeolite catalystmanufactured according to the method for manufacturing the zeolitecatalyst according to an exemplary embodiment of the present disclosurewill be described with reference to FIG. 23.

FIG. 23 is a block diagram of an exhaust gas purification device towhich the zeolite catalyst according to an exemplary embodiment of thepresent disclosure is applied.

As shown in FIG. 23, an exhaust gas generated from an engine 10sequentially passes a turbocharger 20, a diesel oxidation catalyst (DOC)device 30, a catalyzed particulate filter (CPF) 40, a spray nozzle 50,and a selective catalytic reduction (SCR) device 60 such that harmfulmaterials in the exhaust gas are removed. Here, the turbocharger 20, theDOC device 30, the CPF 40, the spray nozzle 50, and the SCR device 60may be installed in an exhaust pipe 70.

The engine 10 includes a plurality of cylinders (not shown) forcombustion of an air mixture. The cylinder is connected with an intakemanifold (not shown) to receive the air mixture, and the intake manifoldis connected with an intake pipe (not shown) to receive external air.

Further, the cylinder is connected with an exhaust manifold (not shown)such that exhaust gas generated during a combustion process is collectedin the exhaust manifold. The exhaust manifold is connected with theexhaust pipe 70.

The turbocharger 20 rotates a turbine (not shown) using energy of theexhaust gas so as to increase the air intake amount.

The DOC device 30 may be provided in a rear end of the turbocharger 20.In the DOC device 30, HC and CO are oxidized and NO is oxidized to NO₂.In addition, in order to effectively generate NO₂, at least one of thezeolite catalyst, which has ion-exchanged with a transition metal and ismanufactured according to the above-described method of the presentdisclosure and a noble metal may be included in the DOC device 30, andthe zeolite catalyst manufactured according to the above-describedmethod of the present disclosure may be used as a supporter of a coldstart catalyst (CSC) that intercalates NOx generated at initialcold-starting in the DOC device 30.

The CPF 40 is provided in a rear end of the DOC device 30, and includesa catalyst filter CPF.

The CPF 40 collects particulate matter (PM) in the exhaust gas andregenerates the collected PM (i.e., soot). The regeneration of soot isperformed when a pressure difference between an inlet and an outlet ofthe CPF 40 is higher than a predetermined pressure.

The spray nozzle 50 is provided between the CPF 40 and the SCR device60, and sprays a reducing agent to exhaust oxidized in the DOC device 30and the CPF 40. The reducing agent may be ammonia, and generally urea issprayed from the spray nozzle 50 and the sprayed urea is decomposed toammonia.

The exhaust gas mixed with the reducing agent and NO₂ generated from theDPC device 30 is supplied to the SCR device 60.

The SCR device 60 is provided in a rear end of the spray nozzle 50, andincludes the zeolite catalyst ion-exchanged with the transition metal,manufactured according to the above-described method of the presentdisclosure. The LTA zeolite catalysts according to various exemplaryembodiments described above may be included in the SCR device 60. Adetailed description of the same components will be omitted. The SCRdevice 60 reduces NO in the exhaust gas to nitrogen gas N₂ using NO₂generated from the DOC device 30 and the reducing agent such that NO_(x)in the exhaust gas can be reduced.

Further, the Cu type of LTA zeolite catalyst according to the exemplaryembodiment of the present disclosure, which can be applied to the DOCdevice 30 and the SCR device 60, may be solely used or mixed with a Cutype of SSZ-13 catalyst. When the Cu type of SSZ-13 catalyst and the Cutype of LTA zeolite catalyst according to the exemplary embodiment ofthe present disclosure are mixed, low-temperature performance andhigh-temperature performance can be more improved.

As described, according to the method for manufacturing the zeolitecatalyst according to the exemplary embodiment of the presentdisclosure, acidity is low and thus the high-temperature performance ofthe catalyst can be improved while reducing the consumption of urea.

While this invention has been described in connection with what ispresently considered to be practical example embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A catalyst comprising linde type A (LTA) zeoliteion-exchanged by copper ions and a copper type of SSZ-13 zeolite,wherein a silicon/aluminum (Si/Al) ratio of the LTA zeolite is 3 to 25,and wherein a mixing ratio of the LTA zeolite to the copper-type SSZ-13zeolite is 1:3 to 3:1.
 2. The catalyst of claim 1, wherein the catalystis coated on a honeycomb carrier or a filter.
 3. The catalyst of claim1, wherein a content of copper in the catalyst is 1 wt % to 5 wt %. 4.The catalyst of claim 1, comprising a substance which is selected fromthe group consisting of an alkali metal and an alkali earth metal,wherein a ratio of the substance to aluminum is 0.1 to 0.3.
 5. Thecatalyst of claim 1, further comprising a substance which is selectedfrom the group consisting of La, Ce, Zr, Sc, and In, wherein a ratio ofthe substance to aluminum is 0.01 to 0.05.